Harmonic influence analysis of unified power flow controller based on modular multilevel converter

The unified power flow controller (UPFC) based on modular multilevel converter (MMC) is the most creative flexible ac transmission system (FACTS) device. In theory, the output voltage of the series MMC in MMC-UPFC can be regulated from 0 to the rated value. However, there would be relatively large harmonics in the output voltage if the voltage modulation ratio is small. In order to analyze the influence of MMC-UPFC on the harmonics of the power grid, the theoretical calculation method and spectra of the output voltage harmonics of MMC are presented. Subsequently, the calculation formulas of the harmonics in the power grid with UPFC are proposed. Based on it, the influence of UPFC on the grid voltage harmonics is evaluated, when MMC-UPFC is operated with different submodular numbers and voltage modular ratios. Eventually, the proposed analysis method is validated using digital simulation. The study results would provide guideline for the design and operation of MMC-UPFC project.

[1]  C. Collins,et al.  UPFC modeling in the harmonic domain , 2006, IEEE Transactions on Power Delivery.

[2]  Jiang Daozhuo.  Control strategy simulation of UPFC based on modular multilevel converters , 2012 .

[3]  Xiao-Ping ZHANG,et al.  Control and protection strategy for MMC MTDC system under converter-side AC fault during converter blocking failure , 2014 .

[4]  Canbing LI,et al.  Optimal allocation of multi-type FACTS devices in power systems based on power flow entropy , 2014 .

[5]  Pan Weiyong,et al.  Nearest Level Modulation for Modular Multilevel Converters in HVDC Transmission , 2010 .

[6]  L. Gyugyi,et al.  The unified power flow controller: a new approach to power transmission control , 1995 .

[7]  Liu Jun,et al.  Modeling of Modular Multi-level Voltage Source Converter , 2011 .

[8]  Guo Jianbo.  Design and Simulation of Unified Power Flow Controller Based on Modular Multilevel Converter , 2013 .

[9]  Zheng Xu,et al.  DC harmonic current calculation for HVDC systems based on the classical transmission line model , 2010, 2010 International Conference on Power System Technology.

[10]  Zheng Xu,et al.  Impact of Sampling Frequency on Harmonic Distortion for Modular Multilevel Converter , 2011, IEEE Transactions on Power Delivery.

[11]  Zheng Xu,et al.  DC-Side Harmonic Currents Calculation and DC-Loop Resonance Analysis for an LCC–MMC Hybrid HVDC Transmission System , 2015, IEEE Transactions on Power Delivery.

[12]  Wang Liqiao,et al.  Harmonic characteristic of sample time staggered space vector modulation for multi-modular or multilevel converters , 2004, 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551).

[13]  Guan Min-yuan.  Mechanism Analysis on the Circulating Current in Modular Multilevel Converter Based HVDC , 2010 .